Binnie's interest in exotic aircraft was rekindled soon afterward, during a combat night patrol over the Persian Gulf. On the horizon, in what was supposed to be a no-fly zone, Binnie saw an unidentified aircraft streaking high and fast toward him. He pulled his F/A-18 into a vertical climb to track the thing, but despite having one of the best long-range radars in the business, he couldn't get a lock. This meant the plane was at extremely high altitude, and as it disappeared over the horizon, moving much too fast to be any kind of stealth fighter or bomber, Binnie watched it go through all the colors of the rainbow – a sign that it was near the outer edge of the atmosphere. He saw the same thing the following night, so he asked around the fleet. He got no answer, and his best guess is that he was seeing one of the long-rumored and top-secret Aurora spy planes, a hypersonic jet thought to have replaced the old Blackbird series. "It gives me confidence," he says, "that there's bigger and better stuff out there that we don't know about."

After the war Binnie was entrusted with all the flying on a $10 billion "dark project" at Point Mugu Naval Base, but when the nineties tech boom hit he hooked up with a start-up called Rotary Rocket, which was trying to develop a reusable manned spaceship for launching telecom satellites. Rotary's idea was to build a big, conical spaceship for two pilots that would reenter the atmosphere with its fat tail down and then unfurl big helicopter blades from its top. The blades would have no engine – they would simply start spinning as a result of the downward drag and eventually slow the vehicle. Minutes before touchdown the pilots would fire tip rockets on the blades and bring the ship in for a soft landing.

The chance to fly a brand new, utterly revolutionary vehicle was like a dream come true to Binnie, and it was a way to finally get into space. Binnie quit the navy and flew the Rotary prototype, piloting the world's first – and probably last - 60-foot-tall conical helicopter. When Rotary ran out of money, Burt Rutan stepped in and offered Binnie his next dream job.

The three big challenges of space flight are getting off the ground, reentering the earth's atmosphere, and landing. NASA's space shuttle needs gargantuan booster rockets to do the first part – the very ones that exploded in the 1986 Challenger disaster – and its reentry speed of 17,800 mph requires the heat-shielding tiles that failed in last year's Columbia tragedy. SpaceShipOne has a more limited mission: It goes only to the edge of space, not into orbit, and it seats only three. But that doesn't make it any less ingenious. After SpaceShipOne reaches its target altitude and starts falling back to earth, the pilot pulls a lever to fold the back half of its wings into what Rutan calls a "feathered" position. Simple aerodynamics flips SpaceShipOne into a belly-first, nose-up fall, with so much drag that the plane floats down slowly, like a badminton shuttlecock, without heating up. Once back in the atmosphere the pilot returns the wings to their normal position and lands SpaceShipOne like a glider.

After so many years in the world's most sophisticated jets, Binnie finds it ironic to climb behind the joystick of a flying a vehicle with fewer electronic components than the X-1 in which Chuck Yeager first broke the sound barrier in 1947. Binnie says, "If somebody had told me when I was in graduate school, 'Brian, in 35 years you'll get a chance to fly the first commercial spacecraft with no computers,' I'd have said, 'I don't think so. People are not going to be that stupid.' "

SpaceShipOne is a shockingly simple machine. The pilot steers with a stick and foot pedals, and most of the flight control surfaces – the wing and tail flaps – are manually driven, using rods and levers. Even bailing out of SpaceShipOne is not complicated: Release nose cone. Climb through hole. Jump.

On September 29, 2004, just three days ahead of the only other close competitor for the X Prize, it will be time to "mount that bull and guide it through the gates," as Binnie says, demonstrating to the world that Scaled Composites has a reliable reusable civilian spaceship, open for business. Once Binnie climbs into that cockpit and tucks his feet into the nose cone, he'll be thinking what he says every test pilot thinks: "Oh, dear God, please don't let me screw up."